If you put the Tabs of a TabPane on Side.LEFT or RIGHT the text in a tab is always rotated, so if you don't want it rotated you need to put the text in a label with tab.setGraphic(), with tabPane.setRotateGraphic(false)

However with side == LEFT or RIGHT I get truncated, centred text in the label, but the close buttons always appear. But if I set the min/max tab width/height to get non-truncated text, the close button only appears on the first tab. Also the screen-width and height are swapped round for LEFT and RIGHT relative to TOP and BOTTOM

See discussion at https://forums.oracle.com/forums/thread.jspa?threadID=2328543